After any valiant effort to clean the car, I enforce strict rules. I announce that the dog is no longer allowed in the main area of the van, and whatever the kids bring in the van, they must bring out.
I'm a real stickler. For a few days. Then my kids break me.

Imagine an apocalyptic scenario with 500 people simultaneously looting a hardware store for the same supplies. You now understand Black Friday. Below are some essential practices that will give you a chance at getting what you want, without risking death.